Index: Ringtoets/Common/src/Ringtoets.Common.IO/ReferenceLines/IReferenceLineReplaceHandler.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r00b160ed6c781f5f20b3697143c255fc498b0ef1
--- Ringtoets/Common/src/Ringtoets.Common.IO/ReferenceLines/IReferenceLineReplaceHandler.cs	(.../IReferenceLineReplaceHandler.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Ringtoets/Common/src/Ringtoets.Common.IO/ReferenceLines/IReferenceLineReplaceHandler.cs	(.../IReferenceLineReplaceHandler.cs)	(revision 00b160ed6c781f5f20b3697143c255fc498b0ef1)
@@ -42,10 +42,10 @@
         /// Replaces the <see cref="ReferenceLine"/> of a <see cref="IAssessmentSection"/>
         /// and propagates the changes to underlying data structure.
         /// </summary>
-        /// <param name="section">The section to be updated.</param>
+        /// <param name="oldReferenceLine">The reference line to be updated.</param>
         /// <param name="newReferenceLine">The new reference line.</param>
         /// <returns>All objects that have been affected by the replacement.</returns>
-        IEnumerable<IObservable> Replace(IAssessmentSection section, ReferenceLine newReferenceLine);
+        IEnumerable<IObservable> Replace(ReferenceLine oldReferenceLine, ReferenceLine newReferenceLine);
 
         /// <summary>
         /// Perform post-replacement updates.
Index: Ringtoets/Common/src/Ringtoets.Common.IO/ReferenceLines/ReferenceLineImporter.cs
===================================================================
diff -u -rfd7a4666e62e74819c8bd9d027deb93b7227be6d -r00b160ed6c781f5f20b3697143c255fc498b0ef1
--- Ringtoets/Common/src/Ringtoets.Common.IO/ReferenceLines/ReferenceLineImporter.cs	(.../ReferenceLineImporter.cs)	(revision fd7a4666e62e74819c8bd9d027deb93b7227be6d)
+++ Ringtoets/Common/src/Ringtoets.Common.IO/ReferenceLines/ReferenceLineImporter.cs	(.../ReferenceLineImporter.cs)	(revision 00b160ed6c781f5f20b3697143c255fc498b0ef1)
@@ -153,7 +153,7 @@
                                3, 3);
             }
 
-            changedObservables.AddRange(replacementHandler.Replace(assessmentSection, importedReferenceLine).Where(o => !ReferenceEquals(o, ImportTarget)));
+            changedObservables.AddRange(replacementHandler.Replace(ImportTarget, importedReferenceLine).Where(o => !ReferenceEquals(o, ImportTarget)));
         }
     }
 }
\ No newline at end of file
Index: Ringtoets/Integration/src/Ringtoets.Integration.Plugin/Handlers/ReferenceLineReplacementHandler.cs
===================================================================
diff -u -r430eba7e8a44c9c9670a3d24d3c02cf94a6b5cfc -r00b160ed6c781f5f20b3697143c255fc498b0ef1
--- Ringtoets/Integration/src/Ringtoets.Integration.Plugin/Handlers/ReferenceLineReplacementHandler.cs	(.../ReferenceLineReplacementHandler.cs)	(revision 430eba7e8a44c9c9670a3d24d3c02cf94a6b5cfc)
+++ Ringtoets/Integration/src/Ringtoets.Integration.Plugin/Handlers/ReferenceLineReplacementHandler.cs	(.../ReferenceLineReplacementHandler.cs)	(revision 00b160ed6c781f5f20b3697143c255fc498b0ef1)
@@ -73,20 +73,20 @@
             return result == DialogResult.OK;
         }
 
-        public IEnumerable<IObservable> Replace(IAssessmentSection section, ReferenceLine newReferenceLine)
+        public IEnumerable<IObservable> Replace(ReferenceLine oldReferenceLine, ReferenceLine newReferenceLine)
         {
             removedObjects.Clear();
 
-            ClearResults results = RingtoetsDataSynchronizationService.ClearReferenceLineDependentData(section);
+            ClearResults results = RingtoetsDataSynchronizationService.ClearReferenceLineDependentData(assessmentSection);
             foreach (object removedObject in results.RemovedObjects)
             {
                 removedObjects.Enqueue(removedObject);
             }
 
-            section.ReferenceLine.SetGeometry(newReferenceLine.Points);
+            oldReferenceLine.SetGeometry(newReferenceLine.Points);
             return new IObservable[]
             {
-                section
+                oldReferenceLine
             }.Concat(results.ChangedObjects);
         }
 
Index: Ringtoets/Integration/test/Ringtoets.Integration.Plugin.Test/Handlers/ReferenceLineReplacementHandlerTest.cs
===================================================================
diff -u -r430eba7e8a44c9c9670a3d24d3c02cf94a6b5cfc -r00b160ed6c781f5f20b3697143c255fc498b0ef1
--- Ringtoets/Integration/test/Ringtoets.Integration.Plugin.Test/Handlers/ReferenceLineReplacementHandlerTest.cs	(.../ReferenceLineReplacementHandlerTest.cs)	(revision 430eba7e8a44c9c9670a3d24d3c02cf94a6b5cfc)
+++ Ringtoets/Integration/test/Ringtoets.Integration.Plugin.Test/Handlers/ReferenceLineReplacementHandlerTest.cs	(.../ReferenceLineReplacementHandlerTest.cs)	(revision 00b160ed6c781f5f20b3697143c255fc498b0ef1)
@@ -178,7 +178,7 @@
             ReferenceLine referenceLine = ReferenceLineTestFactory.CreateReferenceLineWithGeometry();
 
             // Call
-            IObservable[] observables = handler.Replace(assessmentSection, referenceLine).ToArray();
+            IObservable[] observables = handler.Replace(assessmentSection.ReferenceLine, referenceLine).ToArray();
 
             // Assert
             Assert.AreEqual(60, observables.Length);
@@ -376,7 +376,7 @@
             AssessmentSection assessmentSection = TestDataGenerator.GetAssessmentSectionWithAllCalculationConfigurations();
 
             var handler = new ReferenceLineReplacementHandler(assessmentSection, viewCommands);
-            handler.Replace(assessmentSection, new ReferenceLine());
+            handler.Replace(assessmentSection.ReferenceLine, new ReferenceLine());
 
             // Call
             handler.DoPostReplacementUpdates();
@@ -400,7 +400,7 @@
             AssessmentSection assessmentSection = TestDataGenerator.GetAssessmentSectionWithAllCalculationConfigurations();
 
             var handler = new ReferenceLineReplacementHandler(assessmentSection, viewCommands);
-            handler.Replace(assessmentSection, new ReferenceLine());
+            handler.Replace(assessmentSection.ReferenceLine, new ReferenceLine());
             handler.DoPostReplacementUpdates();
 
             // Call